In some known cutting tools, a tool body is provided with an insert support seat, to which a cutting insert is attached, and a cutting edge is formed by the cutting insert.
The insert support seat of a cutting tool of this type is provided in a tool body by directly machining the tool body or machining a separate component called a locator and fixing the locator to the tool body.
The insert support seat includes a major seat surface that supports a bearing surface of the cutting insert, a seat side surface that supports a side surface of the cutting insert, and a thinned portion that is continuous with the major seat surface and the seat side surface.
The thinned portion is provided for the purpose of avoiding interference with the tool body of a cutting edge located at a position at which the cutting edge does not contribute to cutting of the cutting insert, and avoiding stress concentration on a corner portion between the major seat surface and the seat side surface and a corner portion between the seat side surfaces.
The insert support seat of a conventional cutting tool is machined using a plurality of tools, for instance, a drill and an end mill selectively, and for an insert support seat in a complicated shape, a sharp edge is left, for instance, at a position where the major seat surface and a thinned portion intersect, or at a position where a seat side surface and a thinned portion intersect, or further at a position where adjacent thinned portions intersect.
An insert support seat in such a shape is described, for instance, in PTL1 and PTL2.